Ostomy collection bags are discreet pouches or bags which are used to collect the liquid, semi-solid or solid output from a stoma, which is an artificial opening in the abdomen of a patient who has undergone colostomy or ileostomy surgery. A stoma is created in the abdomen wall when a patient has suffered from a bowel obstruction, inflammatory bowel disease, faecal incontinence, trauma, cancer or the like and it enables the bowels to empty.
Ostomy bags can be closed bags that have to be changed 2-3 times a day or alternatively they may be drainable bags that are drained frequently and are then changed every 2-3 days. They contain a filter that allows flatus to be released through a charcoal layer that helps to remove faecal odour.
The composition and odour of faeces varies with diet and moreover the chemistry of the odour emanating from faeces is chemically complex. One cause of faecal odour is due to the presence of a family of sulphur based chemicals known as mercaptans. Other major chemical groups that contribute to the odour are indoles and skatoles, both of which are large cyclic organic compounds.
Filters suitable for use in ostomy bags have been made from microporous activated carbon. The British Standard Test for filter performance challenges the filter with hydrogen sulphide gas. In order to pass and exceed the requirements of the test, chemical treatment of the carbon with, for example, copper, chromium, manganese or iron salts has been necessary. The salt is impregnated and deposited in the microporous activated carbon. Whilst the salt deposited on the surface of the carbon interacts chemically with the hydrogen sulphide and thereby removes it, the impregnating and deposited salt blocks the surface of the carbon with the result that the pores in the body of the structure are much less available to other chemical species for adsorption. Consequently, other odour causing chemicals are not adsorbed so efficiently.
It has now been found that, by selecting a specific mixture of a chemically modified particulate activated carbon and an unmodified particulate activated carbon and impregnating the mixture into a matrix or substrate a filter can be constructed that is very effective in removing the different groups of odour-producing chemicals when the filter is incorporated in an ostomy bag. Alternatively, such a filter can be incorporated into a dressing for application to odour-producing wounds, or into fluid collection devices used to collect infected bodily fluids, such as wound exudates. The filter according to the invention may also be used in respirators, filters used in air conditioning units, for buildings or vehicles as well as for deodorising sewage plants.